Water flood projects are a common approach to enhance oil recovery. Water typically is obtained from an aquifer or from the sea. The water is transported to an injection well site by surface facilities including pumps, filters, water treatment equipment and flow lines. At the injection well site, the water is injected into the desired formation that is to be water flooded.
In some environments, the reservoir to be treated by water flooding is positioned below a suitable source of water in the form of a subterranean aquifer. Several techniques have been employed to “dump flood” water from the upper aquifer or/well zone into a lower interval or well zone at a location designed to enhance oil recovery from an oil reservoir. Various techniques have been used to dump flood water from one well zone into another well zone. For example, electric submersible pumping systems have been inverted and installed below the upper zone interval. Water from the aquifer is drawn into the pump intake of the electric submersible pumping system and discharged downwardly into tubing strung into a lower zone packer, thus injecting water into the desired, lower interval. Locating the inverted electric submersible pumping system below the upper interval can pose additional risk from solids production settling onto the pumping system, which can hinder retrieval of the pumping system.
Attempts have been made to use a variety of other techniques and equipment for dump flooding water into a lower well zone. For example, systems have been designed to draw fluid to a surface location and to pump fluid back downhole to the desired well zone. Additionally, rod pumps have been employed, and electric submersible pumping systems have been proposed for combination with relatively complex Y-blocks for redirecting flow to the lower well zone. However, each of these approaches suffers from various drawbacks, including lower efficiency, increased space requirements, reduced injection rates, added complexity, and other drawbacks.
Other proposals have been made to utilize the natural reservoir pressure for dump flooding a lower well zone. If, for example, the natural pressure in the aquifer is higher than the pressure of the injection zone, the higher pressure can be used to drive water downwardly into the desired, injection zone. However, natural dump flooded wells can be difficult to control. In some applications, restrictors or chokes are installed by intervention or as part of the completion, but such approaches rely heavily on the specific environmental conditions and also increase the difficulty of controlling the injection of water to enhance oil recovery.